The long-term goal of the applicant is to elucidate the mechanisms of placental amino acid metabolism and regulation using newly developed in vitro models. This knowledge will contribute to understanding the relationship between placental metabolism and normal fetal growth and development. The proposed study focuses on elucidating the pathways of placental metabolism of the quantitatively important amino acid glutamate. The human placenta accumulates glutamate to concentrations orders of magnitude above those in either maternal or fetal circulations and acts as a barrier to transplacental glutamate movement. The placenta may provide an important protective system for a compound which is a known fetal neurotoxin. Our fundamental hypothesis is that the glutamate concentrative activity is accompanied by a high rate of glutamate metabolism by the placenta and that the underlying metabolic pathways respond to environmental and regulatory mechanisms. Unique strengths of the project are that 1) it brings together the expertise of two laboratories, one experienced in trophoblast cell culture and cytologic investigation and the other experienced in the study of placental nutrient transport and metabolism 2) it the use of a trophoblast culture model which possesses previously unavailable features of cell differentiation to study metabolic pathways. The specific aims of the project are: 1) Characterization of the trophoblast culture model. 2) Elucidation of the pathways of placental glutamate metabolism. 3) Characterization of regulatory factors of glutamate metabolism. 4) Elucidation of cellular features to support a putative fetal-placental substrate cycle involving glutamate. The specific aims are directed toward achieving the long-term goal of the applicant which should help to increase chances for positive fetal outcomes.